The development of high tech fabrics has permitted the incorporation of fabric into a wide variety of applications not previously consider appropriate for fabrics. For example, certain high tech fabrics have been developed that incorporate elastomeric elements, such as a weave of multifilament yarns and elastomeric monofilaments. These fabrics provide remarkable load bearing characteristics, while at the same time providing appropriate elasticity to be comfortable as a load bearing fabric in seating applications. These fabrics are now widely used to form the seats and backs of office chairs and other seating structures. To enable attachment of the fabric to a chair seat or other support structure, it is known to mold a mounting component (“carrier”) directly onto the fabric. The mounting component is typically molded about the periphery of the fabric to provide a structure that can be mounted to a frame or other support structure. In many applications, it is desirable to mount the fabric to the chair in a stretched (or loaded) condition primarily because the stretched fabric provides more desirable comfort characteristics. The desire to have a loaded fabric complicates the manufacturing process—at least with respect to the process of molding the mounting component onto the fabric.
One known process for manufacturing chair components with a loaded fabric is to stretch the fabric before it is placed in the mold for forming the mounting component. In one known embodiment of this process, the fabric is stretched prior to molding using a stretching machine that is located remotely from the mold. Once stretched, the fabric is shuttled to a loom station where a loom is closed onto the fabric to hold it in the stretched condition. The loom is then moved to the mold and positioned so that the fabric is properly oriented with respect to the mold surfaces. The mold is closed about the fabric while it continues to be held in the stretched position by the loom. Once the molding process is complete, the loom carrying the fabric and attached mounting component are removed from the mold and returned to the loom station. The loom is removed at the loom station and the fabric and attached mounting component are returned to the operator. The assembly is finished, for example, by trimming the excess fabric from the assembly.
A number of other methods are known for forming a molded edge onto a load bearing fabric. In one alternative, the fabric is stretched by the closing action of the mold. In this alternative, the edges of the fabric are held and the mold parts are specially shaped so that movement of the mold parts together causes the fabric to stretch. This process requires a specific amount of stretch to be built into the shape of the mold and does not provide the ability to readily adjust the stretch. In another alternative, hydraulic components are included in the mold. The hydraulic components are moved after the fabric has been closed in the mold to apply the desired amount of stretch. Although providing some benefits, these alternative methods continue to suffer from a variety of problems ranging from high cost to product quality issues.
In another known system for molding a peripheral carrier around a fabric blank, the fabric stretching assembly is integrated into the molding apparatus. The stretching assembly may be disposed about the mold and includes a plurality of clamp assemblies to grip essentially the entire periphery of a fabric blank. The clamp assemblies are selectively movable away from one another on slide assemblies to stretch the blank. When it is desirable to mold a carrier around a generally rectangular fabric blank, the apparatus may include four clamp assemblies and four slide assemblies disposed in a rectangular arrangement outside the mold. The clamp assemblies may grip along the four edges of the rectangular fabric blank. The stretching assembly may include a float plate that is movable with respect to the mold so that the mold does not interfere with the stretching process. The float plate carries the slide assemblies and clamp assemblies and is movable between a stretch position and a mold position. In the stretch position, the float plate is positioned away from the mold so that the fabric is not in contact with any portion of the mold during the stretching process. In the mold position, the float plate is positioned over the mold with the fabric closed between the two mold parts.